Dementia is often preceded by an earlier phase called mild cognitive impairment (MCI), where an individual is still able to live independently, but notices changes in at least one area of cognition, such as memory or language. Early diagnosis presents an important window of opportunity for treatment, personal planning, and decisions about medical care. When medications are discovered that can significantly slow or even halt disease progression, it will also open up a critical timeframe for intervention.
Research has made significant gains in predicting who will progress from MCI to Alzheimer’s disease. Now research is showing promise in identifying those who will advance from MCI to dementia with Lewy bodies (DLB).
Laura Bonanni and colleagues studied 47 individuals with mild cognitive impairment over 3 years, 21 of whom had one of the diagnostic symptoms of DLB. Depending on which cognitive domain was impaired, individuals were classified as amnestic MCI (memory impaired), or non-amnestic MCI (other cognitive domains impaired, but not memory). An additional 50 individuals with DLB, 50 with Alzheimer’s disease, and 50 healthy individuals were included in the study.
All individuals were assessed with standardized measures of cognition, parkinsonism and neuropsychiatric symptoms. They also underwent two brain imaging tests, and lumbar puncture to further identify the underlying cause of their symptoms.
Participants received an electroencephalograms (EEG) at the beginning of the study and again 3 years later. An EEG is a test that measures and records electrical activity in the brain with the patterns of these brain waves in various locations of the brain varying for different medical conditions. The EEG results were analyzed for any quantitative (measurable) differences. Five different patterns emerged.
At the start of the study, all individuals with Alzheimer’s disease and healthy controls were classified as normal, or pattern 1. There was clear distinction between individuals with fully developed Alzheimer’s disease compared to those with DLB. Individuals with MCI fell into pattern 1 (normal), and patterns 2 and 3 (abnormal). Pattern 1 also included more individuals with MCI and subjective memory loss (called amnestic MCI). All patients with Alzheimer’s disease were classified as pattern 1, while those with DLB were classified only as patterns 2, 3, 4 and 5.
After 3 years, 34 of those with MCI had progressed to dementia; 20 of them fulfilled the criteria for DLB and were categorized as MCI-DLB. Another 5 individuals were diagnosed with other neurodegenerative conditions, all of whom had normal EEG results identified as pattern 1. The remaining 8 individuals remained at the MCI stage and were considered non-converted, identified as MCI-NC.
After three years, the EEG patterns of all of the MCI-DLB subjects had changed from their initial pattern. As with the initial EEG, none of them displayed pattern 1. This suggests that EEG patterns in this study for those who progressed to DLB were 100% predictive. Interestingly, when comparing the individuals with MCI and also one diagnostic symptom of DLB, qualitative EEG results provided an even better predictive value of who would progress to DLB than the clinical symptoms.
Conversely, thirteen out of 14 of those classified as MCI-AD were again categorized as pattern 1 at the end of 3 years. This demonstrates that individuals with Alzheimer’s disease largely have a stable EEG results as the disease progresses from MCI to Alzheimer’s disease.
This study also revealed a new EEG pattern that was highly predictive of those who would later develop fluctuating cognition, one of the core features of DLB. Clinical assessment of cognitive fluctuations is challenging in DLB and this study identifies a potentially new means of detection.
Another opportunity presented by this study is the potential of diagnosing DLB at the MCI stage, before other diagnostic symptoms are apparent. All MCI-NC subjects who did not develop dementia after 3 years but who had an EEG pattern other than pattern 1, also had either a positive scan for dopamine transporter loss or presented with REM sleep behavior disorder, both of which are suggestive of early DLB.
In conclusion, it is likely that individuals with MCI and EEG abnormalities observed in this study and who convert to dementia will have DLB. While promising, these findings must be replicated by other research groups before qualitative EEG can be considered a tool to predict the development of DLB.
This study, Qualitative electroencephalogram utility in predicting conversion of mild cognitive impairment of dementia with Lewy bodies was published in the January, 2015 issue of Neurobiology of Aging.